Effect of Overexpression of NtCaM10 on Tobacco Growth and Potassium Absorption under Low Potassium Stress

This research aims to explore the physiological and molecular mechanisms involved in overexpression of NtCaM10 gene on growth and potassium uptake of tobacco under low potassium stress. The experiment adopted wild type (WT) K326 and overexpression of NtCaM10 transgenic tobacco as experimental materials and consisted of two potassium levels, i.e. 5 mmol/L (normal potassium) and 0.15 mmol/L (low potassium). The expression pattern and promoter activity of NtCaM10 gene under low potassium stress were analyzed. The physiological and biochemical indexes, the relative expression of genes related to potassium uptake and the content in different parts of tobacco plants under low potassium stress were determined. The results showed that the relative expression of NtCaM10 gene was significantly increased and the promoter activity was highly initiated after low potassium stress. Under low potassium level, the fresh weight and root length were significantly reduced in WT or transgenic lines compared to the control, and the WT growth was evidently hindered. Compared to WT, the fresh weight and root length of three transgenic lines overexpressing NtCaM10 were significantly increased by 57.44% and 35.77%, respectively. In the transgenic lines, the accumulation of MDA was significantly lower, while the activities of SOD, POD, and CAT were significantly higher than WT. Compared with WT, the average relative expression levels of NtHAK1, NtHAK5, NtKC1 and NtNKT2 in NtCaM10 overexpressed tobacco were significantly upregulated, and increased by 56.60%, 81.84%, 98.08% and 638.89%, respectively. Whereas, the potassium accumulation in root and shoot of tobacco overexpressed NtCaM10 was significantly increased by 21.59% and 32.36% compared to WT. The NtCaM10 gene is involved in the response of tobacco plants to low-potassium stress, and overexpression of NtCaM10 can positively regulate tolerance of tobacco to low-potassium stress by modifying the activities of antioxidant enzymes and the expression of genes related to potassium absorption and transport.